Warm metalworking for plastic manufacturing in brittle semiconductors

Semiconductors are the core of modern electronics¹. Because of their brittleness, semiconductors are usually processed by the complicated techniques of sputtering or deposition^2-4, instead of the effective and versatile metalworking methods like rolling, extrusion and pressing used with metals⁵. Here we show that brittle semiconductors can be plastically manufactured with an extensibility as large as ~3,000% using warm metalworking, that is, plastic manufacturing at slightly elevated temperatures (empirically below 500 K). Many bulk brittle semiconductors, such as Cu₂Se, Ag₂Se and Bi₉₀Sb₁₀, can be processed like metals below 400-500 K into free-standing, large and high-quality films with a thickness from the macro-scale to the micrometre scale. A model based on temperature-dependent collective atomic displacement and thermal vibration is proposed to explain the superior plasticity. The warm-metalworked films can retain the excellent and tunable physical properties of the bulk versions, such as a high carrier mobility up to ~5,000 cm² V^-1 s^-1 and tunable electrical conductivities over six orders of magnitude by adjusting the chemical composition. A case study in film thermoelectric devices demonstrates ultra-high normalized output power densities of 43-54 μW cm^-2 K^-2. This work suggests that brittle semiconductors can be manufactured by warm metalworking for applications in various electronics.